The present invention relates to hydraulic pumps, and in particular to fixed clearance hydraulic pumps of the type including a pair of inter-engaging rotary pump elements such as gears and the like.
High pressure hydraulic pumps that include gear-type rotary pump elements are well-known and typically include a pump housing having a gear chamber therein that is in fluid communication with an inlet and an outlet. In addition, these pumps typically include a pair of parallel shafts journaled within the gear chamber and each including a meshing gear fixedly attached or integrally molded therewith. One of the shafts constitutes an idler shaft that is completely disposed within the housing, while at least one end of the other shaft extends outwardly from the housing for connection with a motor unit or other apparatus for imparting rotary motion to the pump.
Heretofore, the gears were typically fixedly attached by means such as locking rings and/or integrally molded with an associated shaft, thereby affecting the size of the gear and the associated shaft. One detrimental effect of utilizing the locking ring to attach each gear to an associated shaft is the associated decrease in the leak path of the gear, thereby effecting the overall efficiency of the pump. Further, these designs are significantly complex, thereby adding to manufacturing costs.
One aspect of the present invention is to provide a hydraulic pump assembly that includes a pump housing having a chamber defined therein, wherein the chamber includes a pair of cylindrically shaped portions each defining at least one end wall, the housing includes an inlet port and an outlet port in fluid communication with the chamber. The hydraulic pump assembly also includes a pair of rotary pump elements disposed for rotation within the cylindrically shaped portions of the chamber, wherein the pair of pump elements cooperate to create a hydraulic pressure. The hydraulic pump assembly further includes a pair of cylindrically shaped shafts each having at least one end face, and disposed within the pair of cylindrically shaped portions of the chamber and within the pair of pump elements. The shafts are fixed for rotation and axially shiftable with respect to the pump elements. A hydraulic fluid within the chamber stabilizes at least one of the axially shiftable shafts such that the end face of the shaft is spaced from the associated end wall of the cylindrically shaped portion of the chamber when the hydraulic pump is in use.
Another aspect of the present invention is to provide a hydraulic pump assembly that includes a pump housing having a chamber defined therein, wherein the housing includes an inlet port, an outlet port, and at least one circulation port in fluid communication with the chamber, and wherein the chamber includes a pair of cylindrically shaped portions each having at least one end wall. The hydraulic pump assembly also includes a pair of rotary pump elements each having a central bore extending therethrough, and a plurality of meshing teeth, wherein the pump elements are disposed for rotation within the chamber, and wherein the pair of pump elements cooperate to create a hydraulic pressure within a portion of the chamber. The hydraulic pump further includes a pair of cylindrically shaped shafts each having at least one end surface, and disposed within the chamber and within the central bores of the pump elements. The shafts are fixed for rotation and linearly translatable with respect to the pump elements. A hydraulic fluid within the hydraulic pump assembly stabilizes at least one linearly translatable shaft such that the end face of the shaft is spaced apart from the associated end wall of the cylindrically shaped portions of the chamber when the pump assembly is in use.
The present inventive hydraulic pump assembly provides a hydraulic pump having an uncomplicated design, that reduces costs associated with manufacturing, assembly and maintenance. In addition, the hydraulic pump assembly is more readily adapted to be reduced in overall size while still providing a significantly high pump efficiency.